There is a set player race trigger. Fade out before you transition, because it aint smooth at all.
With layouts using the ui editor, you can instance a command card besides the one used by default. then with triggers you can hook it to a unit group and it will always use that unit group. thats enssentially how the coop top bar and the spear of adun is done
you can create a brand new frmae of layouts of type unitstatus bar which will be hooked to a unit and will track its vitals.
no idea about announcers.